Process for the treatment of soot particles and the cleaning of exhaust gases of an internal combustion engine and apparatus for its practice

ABSTRACT

Heretofore, soot particles are removed from exhaust gases of an internal combustion engine by means of a ceramic filter, which must periodically be replaced, namely, each time it is used up. The new apparatus is to remove soot particles continually from the exhaust gases without diminishing the filtering action. In a two-part casing there are provided for the exhaust gases, in a first casing half with the inlet and in a second casing half with the outlet, a first deflector chamber for the exhaust gases. In the first casing half there is located a quiescent zone for the exhaust gases and--surrounded by the two casing halves--a heating system which is flown through three times by the exhaust gases. The apparatus produces a strong combustion of the soot particles present in the exhaust gases and is not subject to any exhaustion, since it does not store soot particles but burn the same as much as possible.

The invention relates to a process for the treatment of soot particlesand the cleaning of exhaust gases of an internal combustion engine andan apparatus for its practice.

West German Laid-open Application 3,502,448 discloses an apparatus forthe removal of soot particles and other solid particles from the exhaustgas of motor vehicles, which apparatus contains a soot collector thatmust be freed of soot through a disposal nozzle. This apparatus has thedisadvantage that it is not operative if the soot collector has becomecompletely filled with soot. The soot collector must be cleaned outperiodically and results in downtimes for the vehicle concerned.

The object of the invention is to provide a process and an apparatus ofthe type mentioned in the introduction, with which it is possiblecontinuously to remove soot particles from the exhaust gas of aninternal combustion engine and to clean the exhaust gas without thenecessity of periodically cleaning a filter.

The invention has the advantage over the prior art in that, duringoperation of the internal combustion engine concerned, its exhaust gasesare continuously freed of soot particles, whereby a filter for residualsoot particles becomes filled with soot only after long operatingperiods. The process brings about and the apparatus permits theelimination of the soot particles and thereafter the destructiveoxidation of the residual hydrocarbon groups and combustion of thecarbon monoxide into carbon dioxide, so that only water vapor, H₂ O, andcarbon dioxide, CO₂, are left as exhaust-gas constituents.

Further advantageous modifications of the invention will become apparentfrom the claims and the ensuing description.

The invention will be explained with reference to practical embodimentsin conjunction with the drawings, in which

FIG. 1 is a perspective view of the apparatus in assembled condition;

FIG. 2 is a perspective exploded diagram of the apparatus;

FIG. 3 is a section through the apparatus in assembled condition;

FIG. 4 is a top plan view of a heating ring associated with theapparatus;

FIG. 5 is a view of a stay for a heating wire.

The apparatus contains, first, a casing 1 (FIG. 1), which consists oftwo casing halves 3, 5 held together by means of flanges 15, 16 andbolts 17. Here, bores with a diameter somewhat larger than that of thebolts are provided in one of the flanges 15. The bolts 17 sit loosely,i.e., with play, in the bores. In the other flange 16, threaded holesare provided into which the bolts 17 are screwed.

Before the two casing halves 3, 5 are brought together, a heating ring 9(FIG. 2) and a flow cone 6 are inserted in the casing 1.

The first casing half 3 (FIG. 3) has an inlet 2 and the second casinghalf 5 has an outlet 22 for the exhaust gases. The flow cone 6 of theapparatus is inserted in the casing 1 such that its tip points towardthe exhaust gases flowing in through the inlet 2 of the apparatus. Gasdeflector plates 7 are provided at one edge 18 (FIG. 2) of the flow cone6. Exhaust gases arriving in the direction of arrow 20 (FIG. 3) along astreamline 19 pass the inlet 2, the space formed between the flow cone 6and the wall of the upper casing half 3, and the gas deflector plates 7(FIG. 3). The gas deflector plates 7 cause the exhaust gases to beswirled in a circular path along the outer wall of the casing 1. Theexhaust gases then pass through the electrically heated heating wires10, 11, (FIGS. 2, 3, 4), clamped in the heating ring 9, at an angle tothe gap between the heating wires 10 and the heating wires 11, afterwhich they arrive in a first deflection chamber 4 in the second casinghalf 5. There, they impinge upon the outer wall of the second casinghalf 5 and, still swirling in a circular path corresponding to the outerwall of the second casing half 5, are deflected in the first deflectionchamber 4. The exhaust gases are also directed toward the outer wall ofthe second casing half 5, since they are deflected beforehand toward theouter wall of the second casing half 5 by an edge 24 spread graduallyoutward on the flow cone 6 .

After deflection of the exhaust gases in the deflection chamber 4, theyare passed for the second time -- again at an angle -- through theheating wires 10, 11 clamped and heated in the heating ring 9, andarrive at the inner surface 23 of the flow cone 6, where they aredeflected -- while still being swirled in a circular ring -- and passedfrom here for the third time -- again at an angle -- through the heatedheating wires 10, 11.

Because the exhaust gases and especially the soot particles pass throughthe heated heating wires 10, 11 three times and in the process sweeppast the heating wires at an angle, intensive heating of the sootparticles, which burn well as a result (pyrolysis), is achieved.

A line 12 leads from the inside of the flow cone 6 out of the firstcasing half 3. The area in which the line 12 discharges into thedeflection chamber 8 in the flow cone 6 constitutes a quiescent zone forthe exhaust gases. From here, residues that remain after the three-stagecombustion can be sucked out of the casing 1. This is accomplishedthrough a line 21 (FIGS. 1, 3), which is connected to a duct 14 in aspace 31 (FIG. 3) disposed downstream from the outlet of the casing 1. Asoot filter 30, preferably in the form of a replaceable filtercartridge, is interposed in the line 21.

During operation of the apparatus, an overpressure develops in the duct14, so that combustion residues, i.e., soot particles, still present atthe outlet 22 are conveyed through the line 21 to the soot filter 30 anddeposited thereat. It can be replaced if the soot filter 30 is saturatedwith soot particles and other combustion residues. A sensor 32connected, for example, to an electronic system (not shown in thedrawings), can monitor the degree of saturation of the soot filter 30.

A duct 13 is used to supply fresh air, which is necessary when theengine adjustment is too rich. The supply of air into the deflectionchamber 4 promotes the second and third combustion of the soot particlesby the heating wires 10, 11. The control of the air supply to the duct13, and thus to the deflection chamber 4, is provided by means known inthemselves. Through another line 25 (FIGS. 1, 2), which also opens intothe deflection chamber 4, a sample of the exhaust-gas stream can betaken directly from the deflection chamber 4 and its condition checkedby means of a sensor.

Gas deflector plates 27 are also provided in the area of the casing half5 (FIG. 3) for the purpose of swirling well the exhaust gases, whichalso entrain soot particles. Other gas deflector plates 37 are installedcentrally upstream from the outlet.

The heating ring 9 bearing the heating wires 10, 11 consists ofrefractory ceramic material. In the practical embodiment, the heatingwires 10, 11 are clamped between spring-loaded stays 26 (FIG. 5). Thespring-loaded stays 26 compensate for changes in length of the heatingwires 10, 11 due to varying temperatures.

In one practical embodiment, the heating wires 10, 11 have developedtemperatures of between 700 and 800° C.

The gas deflector plates 7 in one practical embodiment are inclined withan angle of attack of approximately 22° C. with respect to the planes inwhich the heating wires are located.

In another practical embodiment, the inclination of all gas deflectorplates 7, 27, 37 can be changed if necessary, e.g., by bending the gasdeflector plates.

The exhaust gases emerge from the casing 1 through its outlet 22 andarrive at an exhaust-gas filter 28 which is known in itself, forexample, a catalyst in the form of a monolithic element.

The operation of an internal combustion engine in conjunction with thedescribed apparatus can be achieved, first, by supplying the ignitionelectrodes, i.e., the heating wires 10, 11, with current, therebyheating them up to high temperature. Only then will the internalcombustion engine be started, thus ensuring excellent treatment andfiltering-out of the soot particles as well as thorough cleaning of theexhaust gases.

The process for the treatment of soot particles and cleaning of exhaustgases of an internal combustion engine consists in moving exhaust gasescontaining soot particles past one or more ignition electrodes heated upto high temperature in order to burn said soot particles, feedingremaining soot particles to a soot filter, and passing the exhaust gasesthrough an exhaust-gas filter. The exhaust gases which first entrain thesoot particles are given a rotary motion so as to remove the same, andthe soot particles are concentrated three-dimensionally by the action ofcentrifugal forces and, optionally, of a quiescent in-flowing zone orzones disposed in the flow path, and are passed from there to a sootfilter. To initiate the combustion of newly arriving soot particleswhich are to be burned, one uses, instead of ignition electrodes, theheat of reaction of the already-burning soot particles and/or of theapparatus for carrying out the process, which has been heated up to hightemperature.

I claim:
 1. A process for the treatment of soot particles and thecleaning of exhaust gases of an internal combustion engine, whichcomprises: sweeping the exhaust gases with the soot particles past aplurality of ignition electrode wires heated up to high temperature forburning the soot particles, concentrating the soot particles by givingthe exhaust gases extraining the soot particles a rotary motion, feedingremaining soot particles to a soot filter, and passing the exhaust gasesthrough an exhaust filter.
 2. The process according to claim 1, whichcomprises providing a quiescent zone in the flow path of the exhaustgas, and concentrating the soot particles in the quiescent zone.
 3. Aprocess for the treatment of soot particles and the cleaning of exhaustgases of an internal combustion engine, which comprises: burning thesoot particles entrained in the exhaust gases by utilizing the heat ofreaction of burning soot particles, concentrating remaining sootparticles by giving the exhaust gases entraining the soot particles arotary motion, feeding remaining soot particles to a soot filter, andpassing the exhaust gases through an exhaust filter.
 4. The processaccording to claim 3, which comprises providing an apparatus forcleaning the exhaust gases in the form of a casing having an inlet, anoutlet and gas deflector plates disposed in said housing, initiating theburning of newly arriving soot particles which are to be burned byutilizing the heat of reaction of the already burning soot particles andthe heat of the apparatus for cleaning the exhaust gas after theapparatus has been heated up to high temperature.
 5. An apparatus forcleaning soot particles from exhaust gases of internal combustionengines, comprising a casing having an inlet, an outlet and a centralregion, an ignition electrode wire mounted in said casing for burningsoot particles, gas deflector plates for swirling the exhaust gasesabout said central region and for concentrating the soot particles insaid central region, filter means disposed outside said central regionfor filtering soot particles, and means for withdrawing the sootparticles from said central region and feeding to said filter means. 6.The apparatus according to claim 5, wherein said casing defines acentral longitudinal axis and includes a first casing half having saidinlet and a second casing half having said outlet, including a firstdeflection chamber, disposed in said casing, a flow cone disposedcoaxially in said casing, said flow cone having gas deflector plates anda second deflection chamber, an ignition electrode, wire for burningsoot particles, and an exhaust gas filter fitted downstream from saidcasing as seen in the flow direction of the exhaust gas.
 7. Theapparatus as set forth in claim 6, wherein the second casing half (5)too is provided with gas deflector plates (17) in an annular space (29).8. The apparatus as set forth in claim 6, wherein the second casing half(5) has further gas deflector plates (37, which are disposed in thecenter of the second casing half (5).
 9. The apparatus as set forth inclaim 7, wherein the casing (1) has a substantially rotation-symmetricalshape.
 10. The apparatus as set forth in claim 9, including a heatingring disposed in a plane in which said two casing halves are connectedto each other, said electrode wire being disposed in said heating ring.11. The apparatus as set forth in claim 10, wherein there are providedin the heating ring (9) a first group of heating wires (10) runningparallel to one another and a second group of heating wires (11) runningparallel to one another, and the first group is disposed in thedirection of flow upstream from the second group.
 12. The apparatus asset forth in claim 11, wherein the two groups of heating wires (10, 11)are offset relative to the longitudinal axes of the heating wires. 13.The apparatus as set forth in claim 12, wherein the longitudinal axes ofthe heating wires (10, 11) are placed at right angles.
 14. The apparatusas set forth in claim 13, wherein a duct (12) is provided which from theinterior of the flow cone (6) is brought out of the first casing half(3).
 15. The apparatus as set forth in claim 14, wherein a duct (13)running to the outside is located in the second casing half (5) and isin flow communication with the first deflection chamber (4).
 16. Theapparatus as set forth in claim 15, wherein there is provided in thesecond casing half (5) a duct (14) running from the outlet (22) to theoutside and disposed transversely to the outlet (22).
 17. The apparatusas set forth in claim 16, wherein the line (22) emerging from the seconddeflection chamber (8) is connected via an external line (21) to a line(14) running to an outlet (22) of the casing (1).
 18. The apparatus asset forth in claim 17, wherein a free edge (24) of the flow cone (6) isspread gradually outward.
 19. The apparatus as set forth in claim 18,wherein the inclination of the gas deflector plates (7, 27) can beadjusted to the planes of the heating wires (10, 11).
 20. The apparatusas set forth in claim 19, wherein said filter means is a soot filterattached between the outer ends of the ducts.
 21. The apparatus as setforth in claim 20, wherein there lies in each of the circuits of theheating wires (10, 11) of the heating ring (9) a switch which isoperated by a control electronic system for the temperature-dependentswitching on and off of the circuit concerned.
 22. The apparatus as setforth in claim 21, wherein, instead of heating wires, a duct-typestructure with depth effect and composed of one or more substances puton for catalytic action is employed.
 23. The apparatus as set forth inclaim 22, wherein the exhaust gas filter (28) is a catalyst.
 24. Theapparatus as set forth in claim 23, wherein the catalyst includes astructure in which also the base material consists only of acatalytically active material.
 25. The apparatus as set forth in claim24, wherein impacting, diffusion or electrostatic deposition areemployed to enrich the soot particles.